I did put small Kammback behind my wagon, also made grill blocking so that there are only around size of palm opening when counted all two openings together, one is for IC other for radiator.
I have done coast down test before and after mods, several of them at several days. At one day I got lot lower rolling resistance calculation, car seemed to coast lot longer even there was no wind, but it is only one day testing, with that test I got cd of 0.429, others were average of cd 0.364.
With mods I got better result, rolling resistance seems to be same, but I did get lot better result for cd, several test average is now cd 0.299.
So I calculated that it would be now 18% (my math is not the best so that can be off) reduction in cd, with grill block and 50cm long kamm back extension, I believe that it can be plausible.
At least wind noise is less and car coasts better at 50mph speeds, but I hope to improve even more.
I hope to get under cd 0.25 eventually, bellypan is then next task, need to cover that parachute like section at rear, rear wheel well covers then, maybe that should get me close.
But I guess under cd 0.3, if that really is true, is already quite a success with a wagon shaped car?
